Project Summary Staphylococcus aureus is a major human pathogen that kills tens of thousands of individuals each year in the United States alone. It is adept at acquiring resistance to antibiotics, exemplified by the methicillin- resistant strains better known as MRSA. Moreover, MRSA is now present in both the hospital and community settings, with MRSA isolates in the latter possessing enhanced virulence properties and afflicting healthy individuals. Meanwhile, the pipeline for new antibiotics against S. aureus has dwindled, creating the urgent need to characterize new druggable targets. One such target is the recently discovered ABC transporter Pmt, which is responsible for the secretion of an important class of staphylococcal exotoxins, the PSMs. PSMs undermine the mechanisms of the innate immune system and help disperse bacteria from biofilm communities, contributing to disseminated disease. However, PSMs are too diverse to target directly with a single agent. Therefore, Pmt provides an alternative target, and blocking Pmt would blunt PSM-associated virulence with the additional potential to be bactericidal due to PSMs accumulating within MRSA. The primary goal of this project is to advance Pmt as a drug target with specific aims to gain fundamental biochemical knowledge of how Pmt secretes PSMs?critical for rationally targeting Pmt?and to establish the technical platforms to exploit Pmt as a drug target.